Regarding ever higher T\(_c\) , transition metal based materials had been sampled and studied, experimentally and theoretically, by 2010, and promising directions were few. Considering possibilities more generally, the favored palette of atomic constituents for higher, possibly room temperature, superconductors had already been presented in two suggestions by Ashcroft. In 1968, while research focused on transition metal compounds, he proposed elemental metallic hydrogen as a very high T\(_c\)  material, [1]} based on (1) its small mass favoring high frequencies, and (2) the vibrating proton, which if not too strongly screened should provide the strong scattering that would be required for pairing at high frequencies. These properties were supported by the BCS Eq. REF , since little of a material-specific nature was understood relating to higher T\(_c\) . Ashcroft understood that it would require high pressure to metalize hydrogen, specifically to break the H\(_2\)  molecular bond to create an “atomic hydrogen metal” and bring strong scattering processes to the Fermi energy. That it would require 500 GPa (five megabar) or more[2]} to break the H\(_2\)  bond may not have been anticipated.
